Bitmagnet -https://bitmagnet.io/ - does exactly that. I left it running for a few weeks and then stopped the crawler. Didn't expect much, but still somewhat disappointed by the garbage it reeled in.
I've had one running for over a year now, it's replaced my usage of regular torrent sites completely, there is a lot of junk, and it gets stale, but it's still a better experience than most of the public trackers out there IMO
I built one with a nice TUI to run on a VPS so I can try and find rare magazine torrents, but Hetzner were upset about it. I need to find it a new home. It was a very good citizen, but it still raised too many flags.
Runs fine at home. I've indexed 20M+ torrents in last few months running it during the day. With Prowlarr (or similar) it could easily replace other indexers.
Anything I don't have! Sometimes I'll find a torrent and no seeds/peers and I'll wonder if there is another torrent out there that has the same files in it somewhere that I can find.
The other day it was trying to track down some older High Times issues that were torrented but the torrent is dead. Last night it was a mag titled Films & Filming which I know is scanned, but I can't find anywhere.